Prediction of frictional pressure loss for multiphase flow in inclined annuli during Underbalanced Drilling operations

In Underbalanced Drilling (UBD) method, it is difficult to predict the equivalent circulation density due to co-existence of three phases which are air, cuttings and drilling fluid. This study presents the application of a developed model inspired from a novel intelligent algorithm namely radial basis function optimized by genetic algorithm (GA-RBF) algorithm to calculate frictional pressure loss of two-phase gasified drilling fluid flow along with cutting as the third phase in inclined wellbore portions. The suggested approach was conducted to extensive data reported in literature and was based on Rate of Penetration (ROP), wellbore inclination, pipe rotation and in situ flow rate of each phase. The results of this study show that the proposed model could reproduce the experimental frictional pressure loss data to an acceptable accuracy due to high correlation coefficient (R2 > 0.99) and very small values of average absolute relative deviation (AARD) (2.166726), standard deviation (STD) (0.038222) and root mean square error (RMSE) (0.008783). Results of this study could couple with commercial drilling simulators to accurately predict the frictional pressure loss of three phase flow.